1. Field of the Invention
The present invention relates to a track access method of a recording medium in an apparatus which can optically record or reproduce information.
2. Description of the Prior Art
In an optical disk as an optical information recording medium, each information track is constituted by small spots as information recording units aligned in line. The information tracks are concentrically or helically arranged on the disk surface. When recorded information is read out and reproduced from the optical disk, a light beam is radiated on the information track while rotating the optical disk, and the light reflected therefrom is detected. In this case, since a light beam spot must be accurately aligned with the information track position, a tracking error of the light beam is detected from the reflected light, and control for maintaining an optical track state is performed.
In a conventional track access method in the optical disk, when control polarities are switched with reference to a tracking error signal, a light beam spot is first moved to a position between two tracks, and is then moved to an adjacent track. When the above operation is performed repeatedly, the light beam spot can be moved onto a desired track position See (SHINKAGUSOUZENTAI S5-4, 1984).
In the conventional track access method, however, when the light beam spot is moved across a plurality of tracks, unidirectional driving force is kept applied to a moving section for an optical head for emitting a light beam, and a moving speed of the light beam spot increases accordingly. Therefore, it is difficult to stop the light beam spot on a target track position. More specifically, in order to guide the light beam spot onto a target track position, the beam spot is stopped before the light beam spot is moved from the current track position to the next, target track position and, normal tracking control is then performed. However, if the moving speed of the light beam spot is too high, it is impossible to stop the beam spot onto the target track position only depending on tracking control gain.